Photoactivation devices irradiate a target substance, site or compound. They are useful in a variety of areas such as oncology, photography, industrial photocuring, and other commercial applications.
Current medical therapies, for example, use photoactivation devices to irradiate photosensitizers (molecules which can absorb light to produce a chemical reaction which would not occur in their absence). In response to light, photosensitizers catalyze oxidation and/or reduction of certain chemical moieties. Such reactions can be identified in skin diseases of phototoxicity in humans, livestock, and experimental animals; light-activated pesticides; and medical treatments including photochemotherapy and phototherapy of jaundice, herpes simplex and psoriasis. It has been shown that photosensitizers can cause cell death, DNA damage, protein damage, membrane damage, mutagenesis, and tumor destruction. Oncologists capitalize on this phenomena by introducing photosensitizers to tumor sites in localized concentrations. The site is subsequently exposed to light resulting in the generation of singlet oxygen which destroys the cancer cells and vasculature.
Photosensitizer chemistry is also used in genetic, proteomic and other biochemical analysis. See, for example, International Application No. WO 01/83502 demonstrating multiplexed assays using photoactive compounds. These assays are based on releasable labels (e.g. fluorescent, electrochemical, etc,) that are connected to targets or probes by cleavable linkages. By using the sensitizer chemistries to cleave the label, detectable signals are generated which can be used to monitor binding or hybridization events such as antibody/antigen reactions, enzyme/substrate interaction, probe/target hybridization, and protein/receptor binding. For purposes of sample handling and general convenience, it is desirable to conduct these assays in a conventional microtiter or multiwell plate.
Various types of light sources can be used to carry out the above mentioned applications. An example of one light-emitting device which may be used in photocuring and phototherapy applications is disclosed in U.S. Pat. No. 5,634,711 (the '711 patent). In the '711 patent, a hand-held portable light emitting device features an array of light emitting diodes and a tapered optical assembly to direct light from the array of light emitting diodes at a photoreaction site.
U.S. Pat. No. 5,445,608 (the '608 patent) also discloses a light emitting device that can be used in phototherapy applications. In the '608 patent, an implantable probe has an array of light emitting diodes mounted on a bar inside the implantable probe. The probe is normally intended to be implanted inside a patient's body to irradiate a treatment site.
Lamps are also used to irradiate photoactive compounds. Lamps however are bulky and generate unwanted heat. Excess heat can damage the target site or fixture. For example, excess heat can melt (or soften) a sample holding structure such as a multiwell plate in multiplexed assays. Excess heat also can destroy the samples within the wells.
Another drawback of excess heat is that each reaction site (e.g., each well of a multiwell plate) receives an unequal amount of light. That is, there is an uneven distribution of light from well to well because the distance between the light source and each well is different. Consequently, the samples contained within the wells receive an unequal amount of light. A uniform distribution of light is desirable in assays that generate varying results based upon their exposure to light.
None of the above discussed light emitting devices provide for the features and advantages of the present invention as described hereinafter. It is therefore desirable to provide an apparatus and method for uniformly delivering separate light to individual wells such that each sample is separately irradiated. Still other advantages of the present invention will become apparent upon reading the following disclosure in combination with the drawings.